1. Field of the Invention
The invention relates to a photometry device that corrects light receiving element outputs for temperature variations.
2. Description of Related Art
A conventional photometry device includes a light receiving element having light shielding pixels and light receiving pixels. The light shielding pixels generate dark current outputs because the light shielding pixels are shielded from light. FIG. 11 shows the relationship between an output from a light shielding pixel and temperature for a conventional photometry device as described in Japanese Patent Application No. 3-235586. The photometry device corrects the output from the light receiving pixels for temperature variations. The correction is performed by subtracting a value corresponding to an output of the light shielding pixels from the output of the light receiving pixels.
The outputs from the light shielding pixels are divided into four temperature groups A, B, C, and D corresponding to four temperature zones. The outputs of the light receiving pixels are corrected for temperature variations by first identifying which one of the temperature groups A, B, C or D has a temperature that most closely matches the temperature of the light receiving pixels. Based on the identified temperature group A, B, C or D, a correction coefficient corresponding to the identified temperature group is read from a memory. Then, a temperature correction value is generated by multiplying a dark correction value corresponding to the outputs of the light shielding pixels of the identified temperature group by the correction coefficient. Finally, the output from the photometry device is corrected for temperature variations by subtracting the temperature correction value from the output of each light receiving pixel of the light receiving element.
The conventional photometry device described above only corrects a dark current temperature variations of the light receiving elements. However, light sensitivity changes of the light receiving elements due to temperature variations are not corrected. Thus, the photometry device continues to generate different outputs for objects with the same brightness due to temperature variations.